Evaluation of the combined risk of sea level rise, land subsidence, and storm surges on the coastal areas of Shanghai, China

Shanghai is a low-lying city (3–4?m elevation) surrounded on three sides by the East China Sea, the Yangtze River Estuary, and Hangzhou Bay. With a history of rapid changes in sea level and land subsidence, Shanghai is often plagued by extreme typhoon storm surges. The interaction of sea level rise, land subsidence, and storm surges may lead to more complex, variable, and abrupt disasters. In this paper, we used MIKE 21 models to simulate the combined effect of this disaster chain in Shanghai. Projections indicate that the sea level will rise 86.6?mm, 185.6?mm, and 433.1?mm by 2030, 2050, and 2100, respectively. Anthropogenic subsidence is a serious problem. The maximum annual subsidence rate is 24.12?mm/year. By 2100, half of Shanghai is projected to be flooded, and 46?% of the seawalls and levees are projected to be overtopped. The risk of flooding is closely related to the impact of land subsidence on the height of existing seawalls and levees. Land subsidence increases the need for flood control measures in Shanghai.     

城市地面沉降的灾害链特征——以天津市为例

以20世纪60-80年代天津地区地面沉降灾害的发展为例,讨论了城市地面沉降灾害的特征,分析了地面沉降引发的次生灾害及其防治问题。结果表明,城市地面沉降灾害主要具有缓释特征、不可逆特征、罪罚特征和灾害链特征,城市地面沉降能够破坏市政设施,引发城市内涝和河流泄洪能力降低,造成地下水质和地质环境恶化,使海平面上升,沿海风暴潮加剧,同时还能造成海拔标高损失等。地面沉降所造成的损失是个巨大的灾害链,损失应当包括硬件和软件,也应当包括当前和远景,以致更深层次的影响。另外,缓释、不可逆的灾链特征对经济发展的布局、远景规划和投资环境影响不可低估;生态地理环境灾害链的影响,其效益损失更难于估计。地面沉降是城市灾害系统中的重要环节,也是城市防灾减灾的重要内容。地面沉降灾害的防治,应当是经济、环境、行政、立法,甚至教育、宣传等各个方面相结合的系统工程。     

廊坊市地下水位下降漏斗的成因

通过对廊坊市地下水漏斗演化过程与逐年降水的相关分析,揭示了地下水位下降漏斗的气象干旱响应模式,即气象干旱促使人类过度开采地下水资源,从而进一步加剧水文干旱、地下水位下降漏斗及地面沉降灾害。在时间序列上,气象干旱呈波浪起伏状特征,而地下水位下降漏斗及地面沉降则表现为缓变性、积累性和不可逆性,气象干旱的阶段性终止并不能阻止地下水位下降漏斗及地面沉降的继续发展与蔓延。同时提出了合理开采地下水、大力开展水循环利用、发展节水农业等对策。     

Amendment to “Analytical Solution for the Convectively-Mixed Atmospheric Boundary Layer”: Inclusion of Subsidence

In Ouwersloot and Vilà-Guerau de Arellano (Boundary-Layer Meteorol. doi:10.1007/s10546-013-9816-z, 2013, this issue), the analytical solutions for the boundary-layer height and scalar evolutions are derived for the convective boundary layer, based on the prognostic equations of mixed-layer slab models without taking subsidence into account. Here, we include and quantify the added effect of subsidence if the subsidence velocity scales linearly with height throughout the atmosphere. This enables analytical analyses for a wider range of observational cases. As a demonstration, the sensitivity of the boundary-layer height and the potential temperature jump to subsidence and the free tropospheric stability is graphically presented. The new relations show the importance of the temporal distribution of the surface buoyancy flux in determining the evolution if there is subsidence.     

Modelling geomorphic response to climatic change

This paper develops a three-step thaw model to assess the impact of predicted warming on an ice-rich polar desert landscape in the Canadian high Arctic. Air temperatures are established for two climate scenarios, showing mean annual increases of 4.9 and 6.5°C. This leads to a lengthening of the summer thaw season by up to 26 days and increased thaw depths of 12–70 cm, depending on the thermal properties of the soil. Subsidence of the ground surface is the primary landscape response to warming and is shown to be a function of the amount and type of ground ice in various cryostratigraphic units. In areas of pore ice and thin ice lenses with a low density of ice wedges, subsidence may be as much as 32 cm. In areas with a high density of ice wedges, subsidence will be slightly higher at 34 cm. Where massive ice is present, subsidence will be greater than 1 m. Landscape response to new climate conditions can take up to 15 years, and may be as long as 50 years in certain cases.     

The summer circulation over the eastern Mediterranean and the Middle East: influence of the South Asian monsoon

The summer circulation over the eastern Mediterranean and the Middle East (EMME) is dominated by persistent northerly winds (Etesians) whose ventilating effect counteracts the adiabatic warming induced by large scale subsidence. The ERA40 dataset is used to study the vertical distribution of these circulation features, which both appear to be reconciled manifestations of the South Asian monsoon influence. As predicted by past idealized modeling studies, in late spring a westward expanding upper level warm structure and subsidence areas are associated with Rossby waves excited by the monsoon convection. Steep sloping isentropes that develop over the EMME facilitate further subsidence on the western and northern periphery of the warm structure, which is exposed to the midlatitude westerlies. The northerly flow and descent over the eastern Mediterranean have maxima in July that are strikingly synchronous to the monsoon convection over northern India, where the weaker easterly jet favors a stronger Rossby wave response and consequent impact on the EMME circulation. The pronounced EMME topography modifies the monsoon induced structure, firstly, by inducing orographically locked summer anticyclones. These enhance the mid and low level northwesterly flow at their eastern flanks, leading to distinct subsidence maxima over the eastern Mediterranean and Iran. Secondly, topography amplifies the subsidence and the northerly flow over the Aegean, Red Sea, the Iraq—Gulf region and to the east of the Caspian Sea.     

海平面上升影响下的上海地面沉降防治策略

本文将海平面上升作为上海地面沉降防治策略研究的一个考虑因素,主要通过分析对比黄浦江外滩防汛墙沉降监测结果与工程沿线区域地面沉降监测结果,以及海平面上升对防汛墙防御能力的影响,得到区域地面沉降对防汛墙沉降作用明显、地面沉降叠加了海平面上升因素将进一步降低城市防洪（潮）排涝能力。在此基础上,提出了考虑海平面上升因素下的未来地面沉降防治策略,包括重大市政工程地面沉降监测预警机制建设、实施地面沉降分区管控、加强地下水资源开发利用管理、建立完善地面沉降监测网络等。     

Climatological features of the global tropical subsidence region based on satellite observations

Consisting of subtropical highs and tropical buffer zone, the global tropical subsidence region is the subsidence branches of Hadley cell, Walker circulation and monsoon circulation which are important com-ponents of the global general circulation. This region is closely connected with Asian monsoon. Based on long-term satellite observations of OLR (Outgoing Longwave Radiation) and HIRS-Tbl2 (the bright tem-perature from High-resolution Infra-red Radiation Sounder Channel 12 (6.7μm)), the climatological fea-tures over the global tropical subsidence region are studied in this paper and the main findings are as follows:1) Based on the physical meaning of satellite observed HIRS-12 and comparison with the satellite ob?served OLR and climatological maps of conventional observations of geopotential height and vertical veloc?ity at 500 hPa from NCEP / NCAR reanalysis data, it was found that HIRS-12 might be the best indicator of the global tropical subsidence region from the satellite observations.2) Using satellite observed HIRS-12, some new climatological features were revealed, especially those related with Asian monsoon.3) Comparing the climatological characteristics of tropical subsidence regions between both hemi-spheres, it was found that the circulation in the Northern Hemisphere is more complicated and much closely related with monsoon circulation than that in the Southern Hemisphere. Sudden decay of subsidence movement before monsoon onsets over the South China Sea revealed by HIRS-12 suggested that in the future study of Asian monsoon, it should be paid attention to not only the development of convection but also the variation of tropical subsidence region. It is very useful to monitor the convective and subsidence movements in the tropics by using OLR and HIRS-Tbl2 have been observed from satellite.     

The depth of the daytime mixed layer at two coastal sites: A model and its validation

A mathematical model of mixed-layer depth based on the thermodynamic analysis of Tennekes (1973) is generalized to include advection and subsidence. The effects of advection on mixed-layer depth have been modelled by setting the model equations in a Lagrangian frame, performing an approximate first integral in order to derive the spatial dependence of the model variables, and using these spatial forms to give a set of Eulerian equations. The effects of subsidence have been modelled by imposing a subsidence velocity on the top of the mixed layer as well as allowing subsidence-induced warming above that layer.The model thus derived consists of a system of non-linear differential equations which may be numerically solved to elucidate the temporal behaviour of mixed-layer depth. The boundary conditions necessary for such a solution are drawn from field studies at two coastal sites: one with a relatively simple coastline and essentially flat land under agricultural use, the other with a considerably more complex coastline, rolling relief and mixed land use (agricultural, parkland and urban). In both cases the modelled evolution of mixed-layer depth is in good agreement with the measured depth.The sensitivity of the model to all the input variables is investigated by examining the dependence of the maximum mixed-layer depth on each of these variables in an artificial set.     

2030年上海地区相对海平面变化趋势的研究和预测

从全球气候变化区域响应角度,依据1912-2000年吴淞验潮站年平均潮位资料,构建灰色线性回归组合模型,并将其与最小二乘法和小波变换相结合,分析以吴淞为代表的上海绝对海平面长期变化趋势和周期变化规律。由此预测2030年上海绝对海平面相对2011年的上升值为4 cm,结合已公布的构造沉降和城市地面沉降、流域水土保持和大型水利工程及人工挖沙导致的河口河槽冲刷、河口围海造地和深水航道及跨江跨海大桥导致水位抬升等叠加效应及其变化趋势,预测2030年上海市相对海平面上升10～16 cm,陆地海平面上升有7个风险分区。     

Modelling the combined impacts of sea-level rise and land subsidence on storm tides induced flooding of the Huangpu River in Shanghai, China

This paper presents a scenario-based study that investigates the interaction between sea-level rise and land subsidence on the storm tides induced fluvial flooding in the Huangpu river floodplain. Two projections of relative sea level rise (RSLR) were presented (2030 and 2050). Water level projections at the gauging stations for different return periods were generated using a simplified algebraic summation of the eustatic sea-level rise, land subsidence and storm tide level. Frequency analysis with relative sea level rise taken into account shows that land subsidence contributes to the majority of the RSLR (between 60 % and 70 %). Furthermore, a 1D/2D coupled flood inundation model (FloodMap) was used to predict the river flow and flood inundation, after calibration using the August 1997 flood event. Numerical simulation with projected RSLR suggests that, the combined impact of eustatic sea-level rise and land subsidence would be a significantly reduced flood return period for a given water level, thus effective degradation of the current flood defences. In the absence of adaptation measures, storm flooding will cause up to 40 % more inundation, particularly in the upstream of the river.     

A comparison of SSM/I and TOVS column water vapor data over the global oceans

Summary This paper presents a comparison of column water vapor (CWV) information derived from both infrared measurements as part of the TIROS-N Operational Vertical Sounder (TOVS) and Special Sensor Microwave/Imager (SSM/I) in an attempt to assess the relative merits of each kind of data. From the analyses presented in this paper, it appears that both types of satellite data closely reproduce the bulk climatological relationships introduced in earlier studies using different data. This includes both the bulk relationship between CWV and the sea surface temperature and the annual variation of CWV over the world's oceans. The TOVS water vapor data tends to be systematically smaller than the SSM/I data and when averaged over the ocean covered regions of the globe this difference is between 2–3 kgm^–2. Using a cloud liquid water threshold technique to establish clear sky values of SSM/I water vapor, we conclude that the differences between TOVS and SSM/I are largely a result of the clear sky bias in TOVS sampling except in the subsidence regions of the subtropics. The clear sky bias is considerably smaller than previously reported and we attribute this improvement to the new physical retrieval scheme implemented by NOAA NESDIS. While there is considerable agreement between the two types of satellite data, there are also important differences. In regions where there is drying associated with large scale subsidence of the atmosphere, the TOVS CWV's are too moist relative to both radiosonde and SSM/I data and this difference may exceed 10 kgm^–2. The explanation for this difference lies in the limitations of infrared radiative transfer. By contrast, in regions of deep convection, such as in the ITCZ, TOVS CWV is systematically lower than the SSM/I CWV. Both TOVS and SSM/I data demonstrate similar kinds of gross effects of large scale circulation on the water vapor except in these subsidence regions where TOVS data leads to an under-prediction of the effects of subsidence drying.With 11 Figures     

The Congo basin zonal overturning circulation

The Gulf of Guinea in the equatorial Atlantic is characterized by the presence of strong subsidence at certain times of the year. This subsidence appears in June and becomes well established from July to September. Since much of theWest African monsoon flow originates over the Gulf, Guinean subsidence is important for determining moisture sources for the monsoon. Using reanalysis products, I contribute to a physical understanding of what causes this seasonal subsidence, and how it relates to precipitation distributions across West Africa.There is a seasonal zonal overturning circulation above the Congo basin and the Gulf of Guinea in the ERA-Interim, ERA-40, NCEP2, and MERRA reanalyses. The up-branch is located in the Congo basin around 20°E. Mid-tropospheric easterly flows constitute the returning-branch and sinking over the Gulf of Guinea forms the down-branch, which diverges at 2°W near the surface, with winds to the east flowing eastward to complete the circulation. This circulation is driven by surface temperature differences between the eastern Gulf and Congo basin. Land temperatures remain almost uniform, around 298 K, throughout a year, but the Guinean temperatures cool rapidly from 294 K in May to about 290 K in August. These temperature changes increase the ocean/land temperature contrast, up to 8 K, and drive the circulation.I hypothesize that when the overturning circulation is anomalously strong, the northward moisture transport and Sahelian precipitation are also strong. This hypothesis is supported by ERA-Interim and PERSIANN-CDR (Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Climate Data Record) data.     

赤道反气旋的合成结构和涡度收支

本文通过普查1979—1983年7—9月在10°S—15°N、90°E—140°E范围内的赤道反气旋活动情况,从中选出15个强度和范围较接近的赤道反气旋进行综合分析,得到它们的平均三维结构特征。结果表明,赤道反气旋是一个暖性的中低层系统。反气旋环流与涡度、散度及垂直运动有较好的配合。在赤道反气旋的低层,环流中心为负涡度区和辐散区,并与下沉运动区相对应,四周为正涡度和辐合区,以及上升运动区。高层正好相反。加热场与垂直运动场有较好的对应关系,中心区是干绝热下沉增温区。对涡度收支的计算表明,中低层有负涡度积累,上层有正涡度积累,局地涡度变化主要决定于散度项、平流项和垂直输送项。      

Past and future plant diversity of a coastal wetland driven by soil subsidence and climate change

On the island of Ameland (The Netherlands), natural gas has been extracted from a dune and salt marsh natural area since 1986. This has caused a soil subsidence of c. 1–25?cm, which can be used as a model to infer effects of future sea level rise. The aims of our study were (a) to relate the changes in the vegetation, and more specifically, in plant diversity, during the extraction period to soil subsidence and weather fluctuations, and (b) to use these relations to predict future changes due to the combination of ongoing soil subsidence and climate change. We characterised climate change as increases in mean sea level, storm frequency and net precipitation. Simultaneous observations were made of vegetation composition, elevation, soil chemistry, net precipitation, groundwater level, and flooding frequency over the period 1986–2001. By using multiple regression the changes in the vegetation could be decomposed into (1) an oscillatory component due to fluctuations in net precipitation, (2) an oscillatory component due to incidental flooding, (3) a monotonous component due to soil subsidence, and (4) a monotonous component not related to any measured variable but probably due to eutrophication. The changes were generally small during the observation period, but the regression model predicts large changes by the year 2100 that are almost exclusively due to sea level rise. However, although sea level rise is expected to cause a loss of species, this does not necessarily lead to a loss of conservancy value.     

The role of radiation in an inversion-capped planetary boundary layer

In an inversion-capped planetary boundary layer (PBL), the structure of the turbulent fluxes as well as the height of the inversion are determined by the interaction of turbulent mixing in the PBL, large-scale subsidence above the PBL and radiational cooling. Here the sensitivity of the inversion height and of the turbulent fluxes due to radiational processes is investigated with the aid of a three-layered model for a well mixed PBL. For an example of the Trade-Wind region, the inversion height (i.e., the difference between surface pressure and pressure at the inversion level) varies between 46 and 257 mb and the surface flux of moist static energy between 417 and 99 W m^-2, if the (mean) radiative net flux divergence for both the inversion and the well-mixed layer is changed over a reasonable range of values. None of the parameterization schemes existing in the literature is able to describe these radiational effects in an appropriate way. This is due to the fact that these parameterizations are either not or not flexibly enough linked to the thermodynamical model parameter. Therefore the demand for an adequate parameterization of the radiational influence in a well-mixed PBL under a subsidence inversion is obvious.     

Atmospheric thermic structure studied by acoustic echo sounder, boundary layer model, and direct measurements

In this work, the thermic structure of the atmospheric boundary layer is analyzed by means of direct measurements with radiosonde equipment, remote exploration with a three-monostatic Doppler sodar, and a boundary layer model of order one-and-a-half. Intercomparisons of radiosonde data, sodar data, and model results are made through the study of radiative nocturnal inversion, subsidence inversion, development and height of the mixing layer, and calculus of the temperature structure parameter. The ability of sodar to find the mixing layer height and to detect stable layers is enhanced when these layers are low enough.     

The morphological response of large tidal inlet/basin systems to relative sea level rise

The morphodynamic response of large tidal inlet/basin systems to future relative sea level rise (RSLR), incorporating both Eustatic sea level rise and local land subsidence effects, is qualitatively investigated using the state-of-the-art Delft3D numerical model and the Realistic analogue modelling philosophy. The modelling approach is implemented on a highly schematised morphology representing a typical large inlet/basin system located on the Dutch Wadden Sea (Ameland Inlet) over a 110-year study period. Three different RSLR Scenarios are considered: (a) No RSLR, (b) IPCC lower sea level rise (SLR) projection (0.2?m SLR by 2100 compared to 1990) and land subsidence, and (c) IPCC higher SLR projection (0.7?m SLR by 2100 compared to 1990) and land subsidence. Model results indicate that, for the 110-year study duration, the existing flood dominance of the system will increase with increasing rates of RSLR causing the ebb-tidal delta to erode and the basin to accrete. The rates of erosion/accretion are positively correlated with the rate of RSLR. Under the No RSLR condition, the tidal flats continue to develop while under the high RSLR scenario tidal flats eventually drown, implying that under this condition the system may degenerate into a tidal lagoon within the next 110?years. The tidal flats are stable under the low RSLR scenario implying that, at least for the next 100?years, this may be the critical RSLR condition for the maintenance of the system. Essentially the results of this study indicate that, as the Eustatic SLR is likely to be greater than the apparently critical rise of 0.2?m (by 2100 compared to 1990), the tidal flats in these systems will at least diminish. In the worst, but not unlikely, scenario that the Eustatic SLR is as high as the IPCC higher projections (0.7?m by 2100), the tidal flats may completely disappear. In either case, the associated environmental and socio-economic impacts will be massive. Therefore, more research focusing on the quantification of the physical and socio-economic impacts of RSLR on these systems is urgently needed to enable the development of effective and timely adaptation strategies.     

A numerical study of the marine stratocumulus cloud layer

A one-dimensional grid-level model including longwave radiative transfer and a level-4 second-order turbulent transfer closure which contains prognostic equations for turbulent quantities, is used to study the physics and dynamics of inversion-capped marine stratocumulus clouds.A set of numerical experiments had been performed to examined the role of sea surface temperature, large-scale vertical velocity, wind speed, and vertical wind shear in the formation and the structure of low-level clouds. For a given sea surface and geostrophic wind speed, stratocumulus clouds can grow higher with smaller large-scale subsidence as less dry air entrains into the cloud. Clouds grow higher with higher sea surface temperature for a given geostrophic wind speed and large-scale subsidence as a result of enhanced moist convection. In high wind speeds, the entire cloud deck is lifted up because of larger surface energy flux. In the budget studies of the turbulent kinetic energy (TKE), the buoyancy term is a major source term when the wind speed and the vertical shear are small across the inversion top. When the wind speed and the vertical wind shear across the inversion top become large, the mixed layer is decoupled into a cloud and a subcloud layer. In the TKE budget studies, the shear generation term becomes an important term in the budgets of the TKE and the variance of vertical velocity.     

面向四维变分资料同化的NSAS积云深对流参数化方案的简化及线性化研究

GRAPES全球四维变分资料同化系统需要积云深对流参数化方案的线性化与伴随方案,直接采用原始复杂参数化方案进行线性化并不可行,需要发展简化光滑方案来减缓非线性与非连续性特征。GRAPES全球模式采用NSAS积云对流参数化方案,积云深对流对环境的反馈主要通过补偿下沉来实现,研究突出补偿下沉作用,忽略降水蒸发、动量反馈等贡献,形成简化方案。采用输入温、湿度廓线加入不同幅度小扰动方法,评估参数化方案计算的温度、比湿时间倾向对输入扰动的敏感性,检验非线性与非连续特征。提出避免或减缓非连续“开关”的方法,在简化方案的基础上发展了简化光滑方案。简化光滑方案与原始积云深对流方案相比,在对流触发上一致,在对流的位温与比湿倾向、降水的时序模拟等方面相似,而在减缓非线性、避免非连续性方面显著优于原始方案。基于简化光滑方案发展的线性化方案表明,对小于2倍分析增量幅度的扰动,线性化方案可以较好地模拟非线性方案的扰动发展。发展的简化光滑方案具有合理性和实用性。